This invention is concerned with the deployment and energization of submergible electric motors downhole.
In cable deployed pumping systems (sometimes referred to as cable suspended pumping systems), downhole pumping apparatus (including a submergible pump driven by an oil-filled submergible electric motor, and other components) is lowered into a well on a weight-bearing (strength) cable and is energized by an electrical cable. The cables may be separate cable structures that are banded together or may be components of a single cable structure. The pumping apparatus is lowered onto a landing device previously installed in the well and is releasably locked thereto.
Occasions arise when it becomes necessary to pull the pumping apparatus from the well. This is normally performed by means of the weight-bearing cable. Sometimes, however, the pumping apparatus becomes lodged in the well, i.e., stuck downhole, and it cannot be pulled from the well via the cable.
Excessive pulling loads applied to a cable cause damage to the cable as well as to components of the pumping apparatus. Moreover, forced detachment of a cable from stuck pumping apparatus frequently allows well fluid to enter the interior of the motor, so that when the pumping apparatus is later retrieved, damage to the motor due to the entry of well fluid must be repaired, or the motor must be replaced, before the well can be made productive again.